I am calling from the Ubuntu's Live CD. Can not boot my computer it says DISK 0 I/O Error!. What does it mean? and how can it be repaired?

I have 2, 500 Gb Hard Disks on my computer and on the first disk i have installed ubuntu and windows 7 , dual booting, but I can not boot in any of the systems , the message says there is no operating system installed.
Please advise.
Thank you.
Narendra.

It means that the BIOS cannot read anything (or anything meaningful) from the Master Boot Record of the first hard drive. It may be that the disc has failed, or that it is physically fine but the contents of the MBR are corrupt.

Have you just installed an OS, or has this error come out of no-where?

You should try a rescue live Distro such as you get on the LXF disk sometimes, or Smart Boot Manager (SBM) which came with (eg) the LXF172 DVD. They should tell you what OS's (if any) are on your various partitions. Depending on results, you should/might then be able to rebuild your MBR.

Unsolved mysteries of the Universe, No 13 :-
How many remakes of Anna Karenina does the World need?

Thank you for your replies!
Its done!
Seems to be working now.
But can not understand why it happened in the first place. I did reduce the boot time to 5 seconds and swapiness to 10.
Reseated the cables and installed Grub with the boot-repair CD!